This chapter will focus on Intermediate System to Intermediate System (IS-IS), which supports the OSI Layer 3, and Border Gateway Protocol (BGP), which is a distributed-backbone, autonomous system-based topology.
IS-IS is defined by ISO/IEC 10589 and was initially developed by the International Organization for Standardization (ISO) in 1992. This development was at the same time that the Internet Architecture Board was developing Open Shortest Path First (OSPF), defined by the Internet Engineering Task Force (IETF) in RFC 1131. IS-IS was initially developed to support the OSI Layer 3 Routing Protocol Connectionless Mode Network Service (CLNS). Integrated